1. Field of the Invention
The present invention relates to an electric double-layer capacitor with improved structure for receiving polarizable electrodes.
2. Description of the Prior Art
An electric double-layer capacitor is desired to be reduced in size and thickness, similarly to other electronic components. Wound type and plate type electric capacitors are known general types of electric double-layer capacitors, and such a plate type capacitor can be suitably reduced in thickness.
FIG. 2 shows an example of a conventional plate type electric double-layer capacitor. This electric double-layer capacitor 1 comprises a gasket 2 of butyl rubber or ethylene propylene rubber and a pair of polarizable electrodes 4 and 5 provided therein and separated by a separator 3. The separator 3 is adapted to prevent electronic conduction between the upper and lower polarizable electrodes 4 and 5 while allowing permeation of ions, and is generally formed by a microporous film of polypropylene or nonwoven fabric impregnated with 50% sulfuric acid. The polarizable electrodes 4 and 5 are made of solid carbonaceous compacts obtained by adding dispersion of chlorosulfonated polyethylene as a binder to activated carbon powder and pressure-forming the same, or by punching them from cloth of activated carbon fiber.
Collectors 6 and 7 for airtightly sealing the polarizable electrodes 4 and 5 are formed by plastic sheets of butyl rubber, ethylene propylene rubber or polyisobutylene supplied with conductivity by including conductive carbon. The collectors 6 and 7 are adhered and fixed to the gasket 2 by coating, e.g., a rubber adhesive agent on both surfaces of the gasket 2 by printing or the like. Since the interior of this element is preferably evacuated and airtightly sealed, the adhesion is generally performed under vacuum conditions.
However, since the aforementioned electric double-layer capacitor 1 employs adhesive agents 8 and 9, a long time is required for complicated operations such as coating and hardening of the adhesive agents.
Further, upon application of the adhesive agents 8 and 9, the collectors 6 and 7 and the gasket 2 are changed in size by swelling of the rubber material, leading to inferiority in workability. Further, the adhered portions are not sufficient in airtightness, whereby an electrolyte is liable to leak or evaporate.